Chain Drive

Chain Drive

INTRODUCTION

The chain drive intermediate between belt and gear drives. in has the major advantage of both belt and gear drives chain drives are used for velocity ratios less then the 10 with chain velocities up to  25 m/s and power ratio up to 125 kw. chain drives are popularly used in the transportation industry such as bicycles, motor cycles and automobile vehicles. they also find wide applications in agricultural machinery, metal and wood working machines textile machinery, building construction and materials handling machinery.

ADVANTAGES AND DISADVANTAGES OF CHAIN DRIVES

Advantages

• They can be used for long as well as short center distance.
• They are more compact then belt and gear drive
• There are no slip between chain and sprocket. So they  provide positive drive
• One chain drive can be arranged in several sprockets.
• Higher efficiency (up to 98%) of he drive.
• They transmit more power than the belt drives.
• Smaller load on the shafts then the belt drives.

Disadvantages

• They require precise alignment of shafts than the belt drives.
• They require proper maintenance.
• Noise operation.
• They require take ups.
• More complicated design.

TYPES OF CHAIN DRIVE

The common types are chains are:

1. Link chains (or welded chains) 

link chains

1. Transmission chains (or rolled chains)

Transmission chains

1. Silent chains (or inverted tooth chains)

Silent chain

All these chains will be discussed, in detail, in the following sections.

   LINK CHAINS  

Link chains, also known as welded load chains, are widely used

• In low capacity hoisting machines such as hoists, winches and hand operated cranes as the main lifting appliances.
• As links for suspending the load from the hook or other device.

Dimensions of link chain 

The main dimension of the link chain shown in the fig.

 dimension of the link chain

Classifications of link chains

1. Depending on the ratio between the pitch and the diameter of the chain bar:
• Short link chains: If t <= 3 d,then the chains are known as short link chains



short link chains

• Long link chains: If t > 3 d, then the chains are known as long link chain

  

   long link chain 

  
  
2. Depending on the manufacturing accuracy:
• Pitched chains: When the permissible deviations from the nominal pitch size is within + or - 0.03 d and outside width is within + or - d, then the chain is called as the pitched chain

  

   pitched chain

• Calibrated chains: When the permissible deviations is within + or - 0.1 d of the nominal size in the pitch and out side width, then the chain is known as calibrated chain.

  

  calibrated chain

CONSTRUCTION OF LINK CHAINS

• Link chains are formed by a oval steel links in the sequence shown in the video.
  
  
  
  
• Links for welded chains are formed by number of methods. mostly forged welding and electrical resistance welding are used.
• In forged welding, a single weld made in a link. In the electric resistance method, the link is made from two butt-welded half-links. the welds are made on straights slides of the links. The resistance welding method produces more accurate chains with increased strength.
• After manufacturing the chains are annealed.

SELECTION OF LINK CHAINS

In link chain, it is extremely difficult to determine the actual stress. because, with respect to external forces of the links are welded chains are staticaly determinate and with respect to internal stress three-fold stress three fold statically indeterminate. Therefore the stresses are determined accurately.

Advantages of link chains

• Good flexibility in all directions.
• Smaller pulley diameters and drums.
• Simple design and manufacture.

Disadvantages of link chains

• Heavy weight
• Susceptibility to jerks and over loads.
• Sudden failure.
• Intensive wear of the link in the joints.